The measurement of blood pressure is a common procedure used in hospitals, clinics and physicians' offices as a tool to assist in diagnosis of illness and monitoring of sick patients, as well as an indicator of the general status of a person's health. In standard non-invasive blood pressure measurement practice, blood pressure is measured using an inflatable cuff that is wrapped about a patient's arm or leg. The cuff is then inflated to provide a certain amount of pressure on the artery in the arm or leg beneath the cuff. The cuff is inflated by air supplied by means of an inflation device, such as a pneumatic bulb or an electric pump, connected to the cuff by a tube or tubes. The systolic and diastolic blood pressures are determined as the air inflating the cuff is slowly released thereby deflating the cuff and reducing the pressure on the artery.
The initial pressure to which the cuff is inflated depends upon the particular patient whose blood pressure is being measured. The pressure to which the cuff is initially inflated will be higher for an adult, than for a child, than for an infant, than for a neonate. The maximum pressure to which the cuff is inflated must be controlled to ensure that the patient is not injured by the pressure. This is particularly necessary when measuring the blood pressure of a neonate. Additionally, as the size of the limbs of an adult male will be greater than the size of the limbs of a child or a neonate, different size cuffs are available. For example, cuffs are available sized for use on large adults, average adults, small adults, children, small children, infants and neonates.
Electronic blood pressure measurement devices are in common use that automatically performs a blood pressure measurement procedure, either upon initiation by a clinician or at selected preprogrammed intervals. In using such automatic measurement devices, the clinician must select the mode of measurement to be used, e.g. adult, pediatric, infant, or neonatal. The clinician must also remember to connect the correct blood pressure cuff to the device before initiating a measurement procedure. Therefore, the potential exists for an incorrect cuff to be inadvertently connected to an automatic blood pressure measurement device that is an improper cuff type may be connected with respect to the patient whose blood pressure is to be measured.
Automatic sphygmomanometers are known that are programmed to identify the particular cuff connected to the sphygmomanometer. For example, in U.S. Pat. No. 6,171,254, Skelton discloses an automatic blood pressure monitor for unattended operation wherein the pressure-time characteristic is monitored during initial pressurization of the cuff to determine the cuff size in use. The cuff size in use is determined by matching the initial pressure-time characteristic measured against a set of predetermined pressure-time characteristics for known cuff sizes that are stored in a microprocessor associated with the automatic blood pressure monitor. Having determined the cuff size in use, the microprocessor controls the inflation process to pressurize the cuff to a preselected pressure for that cuff size and deflates the cuff in accord with a preselected deflation sequence for the particular size cuff in use.
U.S. Pat. No. 4,501,280, Hood, Jr., discloses an automated blood pressure monitor adapted to use a variety of cuff sizes, including neonatal, wherein the time of propagation of an acoustical pressure pulse through the cuff and back to a pressure transducer in the monitor is used to verify the type of cuff in use in connection with the monitor. Prior to execution of a blood pressure measurement routine, the cuff is inflated to a given pressure, whereupon a pressure control valve is opened thereby creating a pressure/acoustical pulse which propagates at the speed of sound through the cuff and back to the pressure transducer in the monitor. The total time of propagation is measured and compared to a predetermined threshold intermediate the typical propagation times of neonatal and adult cuffs, respectfully.
U.S. Pat. No. 5,060,654, Malkamaki et al., discloses an automatic identification method for the cuff of a sphygmomanometer wherein a pressure pulse is trigger from a valve upstream of the cuff to a pressure sensing element downstream of the cuff. The pulse width is measured and compared with a predetermined pulse width threshold value to distinguish between a smaller cuff and a larger cuff.
U.S. Pat. No. 5,003,981, Kankkunen et al., discloses a method for identification of the cuff being used in connection with a non-invasive automatic sphygmomanometer wherein a flow restriction means, such as an orifice, is disposed in the tube from the pump to the cuff. To identify the cuff in use, the cuff is rapidly inflated to a pressure of 20–30 mmHg. The inflation is abruptly stopped and the change in the pressure differential across the flow restriction means is monitored as the pressure downstream and upstream of the flow restriction means equalizes. A control element identifies the size of the cuff on the basis of data received from the sensor.
U.S. Pat. No. 6,450,966, Hanna, also discloses a method for automatically identifying a given cuff out of a plurality of cuffs wherein a different flow restrictor is associated with each cuff type. Prior to a blood pressure measurement procedure, the cuff is at least partially and then deflated through the flow restrictor. A pressure measurement is taken downstream of the flow restrictor during the deflation process and this pressure measurement is used to identify the particular type of cuff in use.
U.S. Pat. No. 5,301,676, Rantala et al., also discloses a method for automatically identifying a given cuff of at least a pair of cuffs wherein a flow restrictor is associated with at least one of the cuffs. Prior to a blood pressure measurement procedure, the cuff is inflated and the pressure magnitude variations sensed both upstream and downstream of the cuff. The sensed upstream and downstream pressure magnitude variations are compared and from this comparison which cuff is connected to the sphygmomanometer is determined.
Although the aforementioned methods of automatically identifying what cuff is connected to an automatic sphygmomanometer are effective, some of these methods require a distinct cuff identification procedure prior to initiation of a blood pressure measurement routine. Some of these methods require that a sensed pressure characteristic associated with the cuff in use be compared to a set of predetermined pressure related characteristics for a respective set of cuffs be preprogrammed into the sphygmomanometer memory for identification of the cuff in use. As such, the method may only be used to identify cuffs for which the required pressure characteristic has been preprogrammed.